R: Stochastic matrix of a graph

get.stochastic {igraph}

R Documentation

Stochastic matrix of a graph

Description

Retrieves the stochastic matrix of a graph of class igraph.

Usage

get.stochastic(graph, column.wise = FALSE, sparse =
      getIgraphOpt("sparsematrices"))

Arguments

`graph`	The input graph. Must be of class `igraph`.
`column.wise`	If `FALSE`, then the rows of the stochastic matrix sum up to one; otherwise it is the columns.
`sparse`	Logical scalar, whether to return a sparse matrix. The `Matrix` package is needed for sparse matrices.

Details

Let M be an n x n adjacency matrix with real non-negative entries. Let us define D=diag( sum(M[1,i], i), ..., sum(M[n,i], i) )

The (row) stochastic matrix is defined as

W = inv(D) M,

where it is assumed that D is non-singular. Column stochastic matrices are defined in a symmetric way.

Value

A regular R matrix or a matrix of class Matrix if a sparse argument was TRUE.

Author(s)

Gabor Csardi csardi.gabor@gmail.com

Examples

library(Matrix)
## g is a large sparse graph
g <- barabasi.game(n = 10^5, power = 2, directed = FALSE)
W <- get.stochastic(g, sparse=TRUE)

## a dense matrix here would probably not fit in the memory
class(W)

## may not be exactly 1, due to numerical errors
max(abs(rowSums(W))-1)

[Package igraph version 0.7.0 Index]